The World Health Organization (WHO) said on Friday it expected all member states to support the scientific study on origin tracing of COVID-19 and refrain from politicizing the process.

"Finding the origins of this virus is a scientific exercise that must be kept free from politics," WHO Director-General Tedros Adhanom Ghebreyesus said during a briefing on the next stage of research on the origins of the virus.

A WHO-led international scientific team delivered a report this March following its mission to the central Chinese city of Wuhan. The report concluded a natural origin was "very likely" and the lab origin, hyped by some U.S. politicians, was "extremely unlikely."

Concerning the second phase of the study, the WHO chief set out next steps including integrated studies of humans, wildlife, captive and farmed animals, and environment.

As well as the novel coronavirus being found in China's Wuhan at the end of 2019, scientific findings have suggested some initial cases in Europe, the U.S. and Latin America, where sewage and blood samples have tested positive.

Tedros pointed out that the global study will prioritize geographic areas with the earliest sign of circulation of the virus, and neighboring areas where other SARS-related coronaviruses have been found in non-human reservoirs.

Adding to that, the newly-established International Scientific Advisory Group for Origins of Novel Pathogens, or SAGO, will extend studies related to animal trace-back activities, with additional epidemiology and molecular epidemiology work, including early sequences of the virus.

"Members of this new advisory group will be selected based on their technical expertise, taking into account geographical representation and gender balance," said Tedros, who also expressed gratitude for letters he received from 48 countries, including China.

"The plan for the next phase of global origins study should be led by member states and agreed upon through consultation," said Zhao Lijian, spokesperson for the Chinese Foreign Ministry, at a Friday press conference.

He stressed the need to continuously search for "possible early cases globally and further understand the role of cold chains and frozen foods in the transmission of the virus."

Zhao hailed the joint WHO-China study report as "scientific and authoritative," adding it has laid the basis for the second phase of global origin-tracing work.